You're right about decentralization, but it can't be the only factor that strengthens Bitcoin, it also gains value overtime which is why many people adopt it, so that factor can't be overlooked, which is why yoi should also acknowledge the fixed supply and demand/supply dynamics. Decentralization makes Bitcoin unique and secure from the control of any government or entity but scarcity and demand contributes to it's value so you can't talk about decentralization and disregard that.
Its very true, only decentralisation does not make bitcoin a valuable item but a series of things that no other cryptocurrency can do or if they do it they cant do it better, but i think bitcoin is valuable because people trust it. It is THE first cryptocurrency people knew about at this big scale and because of it being the first cryptocurrency it is trusted by everyone. There can easily be another crypto that is same like bitcoin but it woldnt suceed as much because people would merely see it as a copy and they wont trust it. So being the first cryptocurrency also gives bitcoin an edge